1. Technical Field
The present invention relates to the technical field of an onboard battery for a vehicle that is mounted to a vehicle such as an automobile and can be used in a cold area.
2. Related Art
In various vehicles such as an automobile, an onboard battery for a vehicle for supplying electric power to a motor and various electrical components is mounted.
In recent years, vehicles such as an electric vehicle (EV), hybrid electric vehicle (HEV), and plug-in hybrid electric vehicle (PHEV) are particularly becoming widespread. In these vehicles powered by electricity, an onboard battery having a high electricity storage function is mounted.
The onboard battery includes a plurality of battery modules. The battery module includes, for example, a plurality of battery cells (secondary batteries) such as a nickel-metal hydride battery or lithium-ion battery, a fixing member that tightens battery stacks in a stacked direction, and a bus bar module that electrically connects the battery cells.
The output performance of a battery cell used in such an onboard battery changes depending on the temperature, and the output performance of the battery cell decreases at low temperature. Thus, when the onboard battery is used in a cold area, necessary output may not be obtained by a motor or the like due to insufficient supply of power to the motor or the like from the onboard battery at low temperatures during winter or the like.
Thus, some onboard batteries to be used in a cold area are provided with a heater so that a battery cell is heated by the heater at low temperatures to enhance the output performance of the battery cell (see, for example, Japanese Unexamined Patent Application Publication (JP-A) Nos. 2013-218792 and 2010-140802).
In the onboard battery described in JP-A No. 2013-218792, a plurality of battery cells is disposed inside a case, a heat exchanging member is attached to each of both sides of the case, a temperature adjusting device is attached to each of ducts disposed respectively on both sides of the case, and a thermoelectric converter is disposed between the heat-exchanging member and the temperature adjusting device. At low temperatures, electricity is applied to each thermoelectric converter to heat a heating medium, and the battery cells disposed inside the case are heated by the heating medium.
In the onboard battery described in JP-A No. 2010-140802, a battery cell is held individually inside each cell cover, and multiple heater wires are disposed in an embedded state in each cell cover on the outer circumference side of each battery cell. At low temperatures, each heater wire is electrified to heat the battery cell held inside the cell cover.